Diagnostic device and method for sensing hydration state of a mammalian subject

ABSTRACT

Timed sensing of collection of saliva in a liquid collection element of predetermined volumetric capacity may be used to determine salivary secretion rate, as may be indicative of state of euhydration or dehydration. Sensing of salivary flow rate may be further augmented by sensing concentration of at least one analyte in saliva (e.g., with an immunochromatographic assay performed in a lateral flow device) in order to determine a state of euhydration or dehydration. Production of saliva may be stimulated, and collected saliva may be analyzed to generate an analyte detection signal that indicative of presence and/or correlative of concentration of at least one analyte in the collected saliva to sense a state of euhydration or dehydration.

STATEMENT OF RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationNo. 61/388,234 filed on Sep. 30, 2010 and U.S. Provisional PatentApplication No. 61/450,977 filed on Mar. 9, 2011, and is also acontinuation of International Patent Application No. PCT/US11/54104filed on Sep. 29, 2011. The entire contents of the each foregoingapplications are hereby incorporated by reference for all purposes.

FIELD OF THE INVENTION

The present invention relates to sensing of physiological conditionsincluding hydration state (e.g., euhydration or dehydration) utilizingsaliva of mammalian subjects.

BACKGROUND

Maintaining appropriate hydration level is critical for health andperformance of humans and other mammals. Water lost through processesincluding perspiration and respiration must be replaced. Fluid losses ofbetween 2-3% of body mass detrimentally affect cardiovascular function,thermal dissipation, and exercise performance. Overhydration can alsodetrimentally affect exercise performance (e.g., due to electrolyteimbalance) and stress a subject's kidneys. Relying upon thirst as afeedback mechanism to trigger demand for fluid intake may not beadequate to maintain an optimal hydration level, since a sensation ofthirst sufficient to cause a subject to drink may not be triggered untilafter the subject is already dehydrated.

One method to assess hydration is to periodically weigh a subject undercontrolled conditions. For example, over a bout of exercise, a reductionin body weight measured nude before and after exercise will indicate astate of dehydration. While nude body weight changes may be used toassess acute changes in hydration status during a single exercise bout,over longer periods of time, body weight changes may be influenced bymany factors other than change in hydration status, such as: foodintake, bowel movements, and changes in body composition. As a result,measurement of body weight over a prolonged period is an inaccurate wayof assessing whole body hydration status. But even in a single bout ofexercise, it may be highly impractical to stop and subject for purposesof measuring nude body weight to assess hydration status.

Other known methods to assess hydration status involve use of testing ofurine or blood. For example, urine specific gravity is a common standardamong certain physicians. For patients that can be monitored over time,total urine output or urine specific gravity may be used as a metric.Hydration status can also be assessed using a blood sample, since anincrease in plasma osmolality can often identify a state of dehydration,but such sensing requires invasive collection of a venous blood sampleby a qualified phlebotomist. In numerous settings, use of urine or bloodfor assessment of hydration status can be highly impractical.

For many reasons, saliva is an ideal choice for development of a rapid,point-of-care diagnostic measurement for dehydration and/or stress. Thesample is easily obtained with minimal invasiveness. No blood must bedrawn. In many cases, it is difficult for an individual or health careprovider to access urine in a patient (especially for the elderly orinfants). Also, urine assessment could be indicative of a prior state ofdehydration because the urine is maintained in the bladder and does notnecessarily reflect a subject's current hydration state. It would bedesirable to provide a convenient device and method for sensinghydration status without requiring use of conventional laboratoryequipment and specially trained personnel.

Detection of a constituent in saliva has been proposed for sensinghydration status, such as in U.S. Patent Application Publication No.2008/0050451 to Mabry (“Mabry”). Mabry discloses an assay deviceembodied in a test strip including a series of reaction zones withmonoclonal antibodies capable of binding salivary amylase in a salivasample, and reagents for colorimetric detection of the resultingantibodies with bound salivary amylase to provide a visual determinationof salivary amylase concentration as a proxy for hydration status.Unfortunately, variations in biomarker level among different samples dueto environmental factors, genetic factors, disease state, or otherfactors, as well as difficulties in obtaining adequate signal to noiseratio to overcome variations in the assay technique, may reduce theability of such assays to reliably assess hydration status.

Another approach to sensing hydration utilizing saliva involves sensingthe viscosity thereof, such as proposed in U.S. Patent ApplicationPublication No. 2007/0048224 to Howell et al. (“Howell et al.”). Howellet al. proposes use of a sensing element embodied in a water-permeablematerial (e.g., blotting paper or cloth) or in a tube, and sensingeither the extent or duration of migration of saliva through a portionof the sensing element (since migration rate is affected by salivaryviscosity), based on the understanding that viscosity of salivacorresponds to hydration status. Unfortunately, various factors canaffect the ability of salivary viscosity to predict hydration status.Such factors include recency of food or beverage consumption or use ofchewing gum (as recognized by Howell et al. at ¶[0149]), or occurrenceof certain disease status affecting salivary viscosity (as recognized byHowell et al. at ¶[0152]). Although Howell et al. propose the use of anenvironmental temperature sensor, an environmental humidity sensor, abody temperature sensor, a user location sensor, or a user activitylevel sensor (e.g., a pedometer) to provide further input regarding theoptimal amount of fluid to be consumed by a user, Howell et al. do notdisclose any means to overcome potential errors in detecting salivaryviscosity as a proxy for user hydration status.

Based on the foregoing, the art continues to seek diagnostic devices andmethods for sensing hydration state of a mammalian subject that areadapted to overcome one or more of the foregoing limitations.

SUMMARY OF THE INVENTION

Certain embodiments according to the present invention relate to timedsensing of collection of saliva in a liquid collection element asindicative of state of euhydration, state of dehydration, or salivarysecretion rate. In certain embodiments, sensing of salivary flow ratemay be further augmented by sensing concentration of at least oneanalyte in saliva (e.g., with an immunochromatographic assay performedin a lateral flow device) in order to determine a state of euhydrationor dehydration. In certain embodiments, production of saliva by amammalian subject is stimulated, collected, and analyzed to generate ananalyte detection signal (e.g., quantitative or qualitative signal)useful for sensing a state of euhydration or dehydration of the subject.

In one aspect, the invention relates to an apparatus for sensing a stateof euhydration, state of dehydration, or salivary secretion rate of amammalian subject, the apparatus comprising: a liquid collection elementarranged for placement in fluid communication with oral mucosa of amammalian subject, the liquid collection element being liquid-permeable,being arranged to transport liquid by wicking, and having a predefinedliquid holding capacity; a substrate arranged to support or engage theliquid collection element, with the substrate having arranged thereon aplurality of electrical contact pairs including a first electricalcontact pair and a second electrical contact pair arranged downstream ofthe first electrical contact pair, wherein the first electrical contactpair is arranged to close a first electrical circuit upon exposure tosaliva when the liquid collection element is placed in fluidcommunication with oral mucosa of the mammalian subject, and the secondelectrical contact pair is arranged to close a second electrical circuitupon exposure to saliva transported though at least a portion of theliquid collection element; a timing element arranged to receive a signalindicative of closure of the first electrical circuit, arranged toreceive a signal indicative of closure of the second electrical circuit,and arranged to generate a first time value indicative of time elapsedbetween the closure of the second electrical circuit and the closure ofthe first electrical circuit; and a signaling element arranged togenerate an output signal indicative of state of euhydration, state ofdehydration, or salivary secretion rate of the mammalian subject basedat least in part on the first time value.

In another aspect, the invention relates to an apparatus for sensing astate of euhydration, state of dehydration, or salivary secretion rateof a mammalian subject, the apparatus comprising: a liquid collectionelement arranged for placement in fluid communication with oral mucosain the mouth of a mammalian subject, the liquid collection element beingliquid permeable, being arranged to transport liquid by wicking, andhaving a predefined liquid holding capacity; a salivary stimulatingagent arranged for placement into the mouth of the mammalian subjectprior to or substantially concurrently with placement of the at least aportion of the liquid collection element in fluid communication withoral mucosa of the mammalian subject; at least one first electrode orsensing element arranged to sense a condition indicative of exposure ofa portion of the liquid collection element to oral mucosa in the mouthof a mammalian subject; at least one second electrode or sensing elementarranged to sense a condition indicative of movement by saliva throughat least a portion of the liquid collection element; a timing elementarranged to be initiated responsive to receipt of a signal from ordetection of change of state of the at least one first electrode orsensing element, and to generate a time value indicative of elapsed timesince said initiation upon receipt of a signal from or detection of achange of state of the at least one second electrode or sensing element;and a signaling element arranged to generate an output signal indicativeof state of euhydration, state of dehydration, or salivary secretionrate of the mammalian subject based at least in part on the time value.

Further aspects of the invention relate to methods utilizing theforegoing apparatuses for sensing a state of euhydration, state ofdehydration, or salivary secretion rate of a mammalian subject.

A further aspect of the invention relates to method of sensing a stateof euhydration, state of dehydration, or salivary secretion rate of amammalian subject, the method comprising: inserting a salivarystimulating agent into the mouth of the mammalian subject to stimulatesaliva flow; placing at least a portion of a liquid collection elementof predefined liquid holding volumetric capacity in contact with oralmucosa of the mammalian subject; detecting a condition indicative ofpresence of saliva on or adjacent to the liquid collection element uponexposure of the at least a portion of the liquid collection element tooral mucosa of the mammalian subject, and responsively starting a timer;detecting a condition indicative of movement of saliva through at leasta portion of the liquid collection element while the at least a portionof the liquid collection element is exposed to oral mucosa of themammalian subject, and responsively storing a time value indicative ofelapsed time since the timer was started; and utilizing the time valueto generate an output signal indicative of state of euhydration, stateof dehydration, or salivary secretion rate of the mammalian subject.

Still another aspect of the invention relates to a method for sensing astate of euhydration or dehydration of a mammalian subject, the methodcomprising: placing at least a portion of a liquid collection element ofpredefined liquid holding volumetric capacity in contact with oralmucosa of the mammalian subject; detecting presence of saliva at first,second, and third positions along or adjacent to the liquid collectionelement with respect to time while the at least a portion of the liquidcollection element is in contact with oral mucosa of the mammaliansubject, to determine a first time value indicative of migration ofsaliva from the first position to the second position, and to determinea second time value indicative of migration of saliva between the secondposition and the third position; and utilizing the first time value andthe second time value to generate an output signal indicative of stateof euhydration, state of dehydration, or salivary secretion rate of themammalian subject. Certain embodiments may further include detectingpresence of saliva at a fourth position along or adjacent to the liquidcollection element, to determine a third time value indicative ofmigration of saliva between the third position and the fourth position.

In another aspect, the invention relates to a method for sensing a stateof euhydration or dehydration of a mammalian subject, the methodcomprising: sensing a condition indicative of rate of migration ofsaliva through at least a portion of a liquid collection element influid communication with oral mucosa in the mouth of a mammalian subjectutilizing at least one sensor in sensory communication with the liquidcollection element, and generating a first signal correlative of thesensed condition; sensing concentration of at least one analyte insaliva received from the mammalian subject, the analyte being selectedfrom the group consisting of secretory IgA, albumin, secretorycomponent, and aldosterone, and generating a second signal correlativeof concentration of the at least one analyte; and utilizing the firstsignal and the second signal to generate an output signal indicative ofstate of euhydration, state of dehydration, or salivary secretion rateof the mammalian subject.

Further aspects of the invention relate to use of the described devicesand methods to diagnose a disease state of the mammalian subject, and/orto detect a side effect of drug interaction with the mammalian subject

In a further aspect, any of the foregoing aspects or features andelements as disclosed herein may be combined for additional advantage.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing interconnection of variouscomponents of a system for sensing a state of euhydration or dehydrationof a mammalian subject via saliva of the subject according to oneembodiment of the present invention.

FIG. 2 is a side cross-sectional schematic view of a portion of a salivacollection element arranged in contact with a saliva collectioninterface device having integral electrodes for use with systems andmethods according to certain embodiments of the present invention.

FIG. 3 is a side cross-sectional schematic view of a saliva collectionelement having integral electrodes, a backing element, and a coveringelement for use with systems and methods according to certainembodiments of the present invention.

FIG. 4 is top plan schematic view of a saliva collection element havingintegral electrodes with a guide channel portion arranged between twoelectrode pairs for use with systems and methods according to certainembodiments of the present invention.

FIG. 5 is a top cross-sectional schematic view of a first apparatus forsensing a state of euhydration or dehydration of a mammalian subject viasaliva of the subject according to one embodiment of the presentinvention, with the apparatus arranged to sense both salivary secretionrate and concentration of at least one analyte in saliva, to provide aquantitative output signal based on salivary secretion rate, and toprovide a qualitative signal based on analyte concentration.

FIG. 6 is a top plan schematic view of a second apparatus (similar tothe apparatus of FIG. 5) for sensing a state of euhydration ordehydration of a mammalian subject via saliva of the subject accordingto one embodiment of the present invention, with the apparatus arrangedto sense both salivary secretion rate and concentration of at least oneanalyte in saliva, to provide a quantitative output signal based onsalivary secretion rate, and to provide a qualitative signal based onanalyte concentration.

FIG. 7 is a top cross-sectional schematic view of a third apparatus forsensing a state of euhydration or dehydration of a mammalian subject viasaliva of the subject according to one embodiment of the presentinvention, with the apparatus arranged to sense both salivary secretionrate and concentration of at least one analyte in saliva, to provide aqualitative output signal based on salivary secretion rate, and toprovide a qualitative signal based on analyte concentration.

FIG. 8 is a top plan schematic view of a fourth apparatus (similar tothe apparatus of FIG. 7) for sensing a state of euhydration ordehydration of a mammalian subject via saliva of the subject accordingto one embodiment of the present invention, with the apparatus arrangedto sense both salivary secretion rate and concentration of at least oneanalyte in saliva, to provide a qualitative output signal based onsalivary secretion rate, and to provide a qualitative signal based onanalyte concentration.

FIG. 9A illustrates a sampling portion of an apparatus for sensing astate of euhydration or dehydration of a mammalian subject via saliva ofthe subject according to one embodiment of the present invention,arranged proximate to a vial of buffer solution prior to contacting of aportion of the sampling portion with the buffer solution.

FIG. 9B illustrates the sampling portion of FIG. 9A arranged proximateto a monitoring portion of the apparatus for sensing a state ofeuhydration or dehydration of a mammalian subject via saliva of thesubject according to one embodiment of the present invention, prior toinsertion of a portion of the sampling portion into the monitoringportion.

FIG. 10 illustrates a sampling portion and a monitoring portion of anapparatus for sensing a state of euhydration or dehydration of amammalian subject via saliva of the subject according to one embodimentof the present invention, with the monitoring portion connected via anelectrical communication cable to the sampling portion.

FIG. 11A illustrates a salivary secretion rate sensing apparatus of asystem for sensing a state of euhydration or dehydration of a mammaliansubject via saliva of the subject according to one embodiment of thepresent invention.

FIG. 11B illustrates a salivary analyte concentration sensing apparatusof a system for sensing a state of euhydration or dehydration of amammalian subject via saliva of the subject according to one embodimentof the present invention, with a liquid collection element thereofarranged proximate to a vial of buffer solution.

FIG. 12 is a line chart embodying values of salivary flow rate (ml/min)plotted as a function of time for a first control group of researchstudy participants, and values of salivary flow rate (ml/min) plotted asa function of percentage body mass loss and time for a seconddehydration group of research study participants, showing thatdehydration is accompanied by a reduction in salivary flow rate (i.e.,secretion rate).

FIG. 13 is a line chart embodying values of secretory IgA concentration(μg/ml) plotted as a function of time for a first control group ofresearch study participants, and values of salivary flow rate (ml/min)plotted as a function of percentage body mass loss and time for a seconddehydration group of research study participants, showing thatdehydration is accompanied by an increase in secretory IgAconcentration.

FIG. 14 is a line chart embodying values of salivary albuminconcentration (μg/ml) plotted as a function of time for a first controlgroup of research study participants, and values of salivary flow rate(ml/min) plotted as a function of percentage body mass loss and time fora second dehydration group of research study participants, showing thatdehydration is accompanied by an increase in salivary albuminconcentration.

FIG. 15 is a flowchart illustrating various steps of a method forsensing a state of euhydration or dehydration of a mammalian subjectincluding stimulating production of saliva of the subject and sensing ofconcentration of one or more analytes in the saliva, according to oneembodiment of the present invention.

FIG. 16 is a top plan view of a sampling portion of an apparatus forsensing hydration state or salivary secretion rate of a mammaliansubject, the sampling portion including a liquid collection elementarranged over a portion of a circuit board substrate having foursequentially arranged electrical contact pairs for sensing presence ofsaliva.

FIG. 17 is a top plan view of a sampling portion of another apparatusfor sensing hydration state or salivary secretion rate of a mammaliansubject, the sampling portion including a liquid collection elementsupported on or in a substrate having a numeric scale and having asocket arranged for interfacing with a separate monitoring portion (notshown).

FIG. 18 is a top schematic view of a monitoring portion of an apparatusfor sensing hydration state or salivary secretion rate of a mammaliansubject, the monitoring portion including an alphanumeric display andother user-perceptible indicators and being intended for use with asampling portion such as described in connection with FIG. 16 or 17.

FIG. 19 is a top schematic view of a monitoring portion of anotherapparatus for sensing hydration state or salivary secretion rate of amammalian subject, the monitoring portion including an alphanumericdisplay, other user-perceptible indicators, and an interface cable, andbeing intended for use with a sampling portion such as described inconnection with FIG. 16 or 17.

FIG. 20A is a top plan view of a sampling portion and a monitoringportion of an apparatus for sensing hydration state or salivarysecretion rate of a mammalian subject, with the sampling portion and themonitoring portion being separated from one another.

FIG. 20B is a side elevation view of the apparatus illustrated in FIG.20A, with the sampling portion connected to the monitoring portion.

FIG. 20C is a bottom plan view of the apparatus illustrated in FIG. 20B,with the sampling portion connected to the monitoring portion.

FIG. 21A is a table summarizing results of five salivary secretion ratesensing tests utilizing a sampling portion with a X5169 collection padand four sequentially arranged electrical contact pairs A to D.

FIG. 21B is a line chart representing time for migration of salivabetween respective electrodes of the salivary secretion rate sensingtests summarized in FIG. 21A, superimposed over a bar chart representingaverage migration times.

FIG. 22A is a table summarizing results of five salivary secretion ratesensing tests utilizing a sampling portion with a D4607 parallelcollection pad and four sequentially arranged electrical contact pairs Ato D.

FIG. 22B is a line chart representing time for migration of salivabetween respective electrodes of the salivary secretion rate sensingtests summarized in FIG. 22A, superimposed over a bar chart representingaverage migration times.

FIG. 23A is a table summarizing results of four salivary secretion ratesensing tests utilizing a sampling portion with a D4607 perpendicularcollection pad and four sequentially arranged electrical contact pairs Ato D.

FIG. 23B is a line chart representing time for migration of salivabetween respective electrodes of the salivary secretion rate sensingtests summarized in FIG. 23A, superimposed over a bar chart representingaverage migration times.

FIG. 24A is a top plan view of a sampling portion of an apparatus forsensing hydration state or salivary secretion rate of a mammaliansubject similar to the sampling portion illustrated in FIGS. 20A-20C,but with addition of two colored polymeric strips or loops as shieldingelements over portions of the liquid collection element in the form of aD4607 perpendicular collection pad, with the liquid collection elementarranged over four sequentially arranged electrical contact pairs A toD.

FIG. 24B is a table providing results of three in vivo stimulatedsalivary secretion rate sensing tests utilizing the sampling portion ofFIG. 24A.

FIG. 24C is a line chart representing time for migration of salivabetween respective electrodes of the salivary secretion rate sensingtests summarized in FIG. 24B, superimposed over a bar chart representingaverage migration times.

FIG. 25A is a top plan view of a sampling portion of an apparatus forsensing hydration state or salivary secretion rate of a mammaliansubject similar to the sampling portion illustrated in FIGS. 20A-20C,but with addition of an notch- or aperture-defining clear polymericshielding element over portions of the liquid collection element in theform of a D4607 perpendicular collection pad, with the liquid collectionelement arranged over four sequentially arranged electrical contactpairs A to D.

FIG. 25B is a table providing results of three in vivo stimulatedsalivary secretion rate sensing tests utilizing the sampling portion ofFIG. 25A.

FIG. 25C is a line chart representing time for migration of salivabetween respective electrodes of the salivary secretion rate sensingtests summarized in FIG. 25B, superimposed over a bar chart representingaverage migration times

DETAILED DESCRIPTION

The present invention relates in various embodiments to sensing ofsalivary secretion rate (e.g., as may be measured by sensing time tocollection of saliva in multiple portions or the entirety of a liquidcollection) as indicative of state of euhydration or dehydration. Asnoted previously, determination of state of euhydration or dehydrationmay be further aided by sensing of at least one analyte in saliva.

Research recently performed by Dr. Neil P. Walsh of the University ofWales (Bangor) School of Sport, Health and Exercise Sciences (assubsidized by the assignee of the present application and not yetpublished) has demonstrated that dehydration is accompanied by areduction in salivary secretion rate, as well as increases in certainanalyte contained in saliva, such as IgA and albumin. FIGS. 13-15 embodyline charts including values of salivary flow rate, secretory IgAconcentration, and salivary albumin concentration, respectively, plottedas a function of time for a first control group of research studyparticipants, and plotted as a function of percentage body mass loss andtime for a second dehydration group of research study participants.Although not verified in the above-mentioned study, Applicants have alsotheorized that dehydration may be accompanied by an increase in salivaryaldosterone concentration may be correlative of dehydration.

In certain embodiments, salivary secretion rate may be measured byplacing a liquid collection element of predefined liquid holdingvolumetric capacity in a user's mouth, measuring the time required tosaturate the predefined liquid holding capacity of the liquid collectionelement, and then dividing the predefined volumetric capacity by theresulting time value (e.g., to yield volume divided by time). Suchsecretion rate may be used to determine state of euhydration, state ofdehydration, state of disease (e.g., where the disease state includeshyposalivation as a symptom thereof), and/or to detect a side effect ofdrug interaction with the mammalian subject. For example, Sjögren'ssyndrome is a chronic autoimmune disease in which a person's white bloodcells attack the person's moisture-producing glands, and such disease ischaracterized by hyposalivation. Detection of salivary secretion ratebelow a predetermined threshold (such as may be optionally validated bymultiple runs of substantially the same type or multiple tests ofdifferent types) utilizing devices and/or methods as disclosed hereinmay be used to diagnose Sjögren's syndrome. Other disease states may bedetected. Similarly, certain drugs are characterized by hyposalivationas a side effect, and devices and/or methods as disclosed herein may beused to detect a side effect of drug interaction with a user (e.g., bycomparison of an output signal or an apparatus disclosed herein, orinformation derived from such signal, with at least one reference valueor reference value range correlative of the side effect of druginteraction). In certain embodiments, dosage and/or administration of adrug may be adjusted in response to the detection of a side effect (suchas hyposalivation) of the drug interaction. In certain embodiments, anapparatus and/or method as disclosed herein may be used to determinesuitability or readiness of a patient to undergo a medical or dentalprocedure that requires or is benefited by maintenance of a particularsaliva secretion rate range or threshold (whether low or high).

In certain embodiments, a process of measuring salivary secretion ratemay be automated through use of a timing element that is activated usingat least one first electrode or sensing element arranged to sense acondition indicative of exposure of a portion of the liquid collectionelement to oral mucosa (e.g., under the tongue) in a user's mouth, andthat is deactivated using at least one second electrode or sensingelement arranged to sense a condition indicative of saturation of thepredefined liquid holding capacity while the liquid collection elementis exposed to oral mucosa in the user's mouth. A time value indicativeof elapsed time since the timer was started may be stored in a memory,and such time value (or a value derived therefrom) may be utilized (atleast in part) to generate an output signal indicative of state ofeuhydration, state of dehydration, or salivary secretion rate of theuser.

In certain embodiments, electrodes and/or sensing elements may bearranged in sensory communication with one or more portions of a liquidcollection element, with a suitable interface (e.g., via electricallyconductive traces, wires, or the like) to processing or control elementsarranged to receive signals therefrom. In certain embodiments, suchelectrodes and/or sensing elements may be deposited on a thin film(e.g., polymeric thin-film) to which a porous or fibrous medium isadhered or otherwise retained. In certain embodiments, complementaryelectrode pairs each define open circuits that are arranged to be closedby conduction of electric current through saliva in contact therewith.Electrical conductivity of saliva may be enhanced by presence of one ormore electrolytes (e.g., sodium chloride) in or on to the liquidcollection element arranged to contact saliva. Various types of sensingelements that may be used include capacitive sensing elements,conductivity sensing elements, optical sensing elements, and the like.

Multiple electrodes and/or sensing elements may be arranged in series,in parallel, or in series and parallel configurations. When multipleelectrodes and/or sensing elements are used, multiple time valuesindicative of migration of saliva to predetermined distances and/or tooccupy predefined volumes may be established. The multiple values may beprocessed and/or compared (e.g., using a processing element and/orcomparator). Multiple time values may be compared or otherwise processed(e.g., to establish a mean value, deviation from a mean value,difference, ratio, etc.), and one or more resulting values may be usedat least in part to establish an output signal.

Since salivary secretion rate, viscosity of produced saliva, and/ormucin interaction may not be uniform during the entire saliva samplecollection period, time values indicative of migration of saliva topredetermined distances and/or to occupy predefined volumes may not beequal for migration of saliva from one sensing region (e.g., circuitclosure region) to the next, even when multiple sensing regions areequidistantly spaced. In certain embodiments, three, four, or moresensing regions are arranged in series, time values indicative ofmigration of saliva between different sensing regions are stored (e.g.,to establish first and second, or first, second and third (oradditional) time values, and an output signal (e.g., indicative of stateof euhydration, state of dehydration, or salivary secretion rate) isbased on at least in part on the multiple values, on a comparisonbetween two or more time values, and/or at least one processed valuederived from the multiple time values.

In certain embodiments, sensing elements are provided in the form ofpaired electrically conductive traces or contacts each having a gapbetween two contacts, with the contacts arranged to close an electriccircuit upon contact with saliva. Such sensing elements are preferablyarranged on a substrate arranged to support or engage a liquid-permeableliquid collection element. Multiple contact pairs may be arranged inseries, such that an advancing front of saliva migrating through aliquid collection element may close a first circuit upon closing the gapbetween a first contact pair, then close a second circuit upon closingthe gap between a second contact pair, and thereafter similarly closecircuits between respective additional (e.g., third, fourth, etc.)contact pairs, with the closure of each circuit being used to affectoperation of at least one timer (or multiple timers) to identifymigration time of saliva through one portion, multiple portions, or theentirety of the collection element.

In certain embodiments, an apparatus as described herein may include anelectrolyte (e.g., arrangeable in, on, or against a portion of a liquidcollection element) to increase conductivity of saliva collected by theliquid collection element.

In certain embodiments, a liquid collection element comprises a porousmedium or a fibrous medium arranged to absorb saliva. A liquidcollection element may be formed of paper, fabric, nitrocellulose, orany other suitable material. Desired dimensions may be 7×21 mm or 10×15mm, so as to provide a collection volume in a range of 100 to 150microliters. In certain embodiments, a liquid collection elementcomprises a lateral flow test strip. In certain embodiments, a liquidcollection element comprises a material having directionally uniformliquid wicking characteristics. In other embodiments, a liquidcollection element comprises a material arranged to wick liquid in onedirection preferentially relative to another direction. In variousembodiments, a liquid collection element includes a wicking element witha preferential flow direction arranged in substantially same directionof intended migration of saliva through the collection element.

In embodiments with a liquid collection element having a preferentialflow direction, first and second electrode or sensing elements may beseparated along a direction through which liquid does not preferentiallywick through a liquid collection element, in order to reduce thepossibility that a frontal edge of saliva advancing within a liquidcollection element may reach a second electrode or sensing elementbefore the liquid collection element is saturated. A liquid collectionelement may further utilize selective placement and/or patterning ofhydrophobic and/or hydrophilic materials in order to guide a frontaledge of saliva advancing therein in order to promote saturation of aliquid collection element before at least one second electrode orsensing element generates a signal indicating such saturated conditionhas been attained.

In certain embodiments, a liquid collection element comprises aliquid-permeable porous medium or fibrous medium that is supported by orotherwise engaged with a substrate. In certain embodiments, a substratemay be arranged in contact with one or multiple surfaces of a liquidcollection element. In certain embodiments, a substrate may be providedas part of a housing or tube (e.g., formable by injection molding, heatshrink tubing, or another method) that surrounds a portion of a liquidcollection element, with another portion of the liquid collectionelement being exposed. In certain embodiments, a liquid collectionelement includes a portion of a porous or fibrous material that issandwiched between liquid-impermeable materials (e.g., polymeric films),with another portion of the liquid collection element having at leastone exposed surface arranged to absorb saliva upon contact therewith. Aportion of a liquid collection element may extend beyond a substratearranged to support or engage the liquid collection element. In certainembodiments, a portion of one surface of a liquid collection element maybe covered with a removable (e.g., hinged) cover arranged to provide abarrier to liquid contacting the second electrode from a face of theliquid collection element, but permitting lateral flow of saliva withinthe liquid collection element. Maintaining a portion of the liquidcollection element isolated from surface contact with liquid reduces thepossibility for liquid to reach a second (or subsequent) electrode orsensing element before the liquid collection element is saturated withsaliva.

In certain embodiments, multiple portions of a liquid collection elementmay be exposed, with the exposed areas separated by one or more liquidimpermeable barriers arranged to limit a tendency of an absorptivesurface or portion of the liquid collection element from being blockedto further liquid flow (e.g., blocking by soft tissue below the tonguethereby sealing or restricting the liquid inlet within a subject'smouth). If provided, such a barrier is preferably raised relative to atleast one surface of the liquid collection element. In one embodiment, abarrier comprises a cover defining multiple apertures.

In certain embodiments, a portion of a liquid collection element may becovered by a removable liquid-impermeable covering element, such as aremovable adhesive tape or other covering element.

A liquid collection element may include one or more reduced dimensionguide channel portions arranged between at least one first electrode orsensing element and the at least one second electrode or sensingelement. The term “channel” in this context does not necessarily requirean open space with the absence of material; instead, a reduced dimensionguide channel portion may contain porous or fibrous material. Since itis advantageous to ensure that a liquid collection element is fullysaturated with saliva before triggering a signal indicating such date,one or more reduced dimension guide channel portions may be used toreduce the possibility that a frontal edge of saliva advancing within aliquid collection element may reach a second electrode or sensingelement before the liquid collection element is saturated.

In certain embodiments, a liquid collection element may include one ormore tubes or channels that are devoid of porous or fibrous material.For example, a liquid collection element may include one or moremicrofluidic channels each having at least one dimension of less thanabout 500 microns. One or more flow regulating elements may be providedin a liquid collection element in order to reduce the possibility that afrontal edge of saliva advancing within a liquid collection element mayreach a second electrode or sensing element before the liquid collectionelement is saturated.

In certain embodiments, a liquid collection element may be arrangedwithin a sample collection portion of an apparatus for sensing state ofeuhydration or dehydration, with other components of the apparatus(e.g., timing element, processing element/comparator, and/or signalingelement, among others) being arranged within a monitoring portion. Incertain embodiments, a sampling portion may be operatively connected toa monitoring portion via an electrical communication cable and anelectrical interface connector, or via wireless communication, therebypermitting the sampling portion to be inserted into the mouth of a userwhile a monitoring portion is spatially separated therefrom. In otherembodiments, a sampling portion may be arranged for insertion into amonitoring portion (e.g., within a slot defined therein) to establishelectrical and/or sensory communication between the sampling portion anda monitoring portion. By providing a sampling portion separate from themonitoring portion, the monitoring portion may be sequentially reusedwith numerous sampling portions of disposable character. A monitoringportion may be arranged to sense salivary secretion rate alone, or maybe arranged to further sense concentration of at least one analyte insaliva such as with an optical reading element. A monitoring portion mayinclude any suitable combination of various components such as (but notlimited to) a battery, a timer, a processing and/or control element, acomparator, a memory, a display, one or more indicator lights, anaudible output element, sensor traces or wires, an electrical interfaceplug, a sampling portion receiving cavity, an optical reading element,and a communication element arranged to communicate (whether in wired orwireless fashion) with one or more terminals or other remotecommunication devices.

In certain embodiments, an apparatus for sensing state of euhydration ordehydration is arranged to generate a user-perceptible output signalindicative of hydration status that is quantitative in character. A userperceptible output signal generated by such an apparatus may be visible,audible, and/or tactile in character. Examples of quantitative signalsinclude salivary secretion rate (e.g., in μl/min or other suitableunits, obtainable by dividing volumetric capacity of the liquidcollection element over measured time to saturation), time to saturatethe liquid collection element (e.g., in seconds), analyte concentrationlevel (e.g., in μg/ml or other suitable units, obtainable via use of anoptical reading element or by comparison of colored bands or coloredposition along an immunoassay test strip calibrated to one or morereference indicator values), and the like.

In certain embodiments, an apparatus for sensing state of euhydration ordehydration is arranged to generate a user-perceptible output signalindicative of hydration status that is qualitative in character. Withrespect to salivary secretion, one or more threshold values for salivarysecretion rate or time to saturate a liquid collection elementindicative of euhydration or dehydration may be stored in memory of theapparatus, and sensed values may be compared to the one or morethreshold values to provide a simple qualitative assessment as towhether a user is in a state of euhydration or dehydration. Aqualitative signal may be selected from two, three, four, or morepossible results. For example, in certain embodiments, a qualitativesignal may be limited to two possible results of euhydration ordehydration. In other embodiments, a qualitative signal may be selectedfrom three possible results of euhydration, dehydration, and severedehydration. In other embodiments, a qualitative signal may be selectedfrom three possible results of euhydration, slight dehydration, moderatedehydration, and severe dehydration. With respect to concentration ofone or more analytes in saliva, output of an optical reading element maybe compared to one or more threshold signal level to provide aqualitative output. Alternatively, presence or absence of a coloredsignal within a window positioned at a specified distance from aconjugate pad of an immunoassay test strip (with a colored signalindicating high concentration of sensed salivary analyte) may provide aqualitative output (e.g., with presence of a colored signal indicating adehydration state, and absence of a colored signal indicating aeuhydration state). A processing element and/or comparator may bearranged to compare at least one time value against at least onepredetermined threshold value, and/or to compare multiple time valuesagainst one another (or a value derived therefrom), and responsivelytrigger a signaling element to generate a user-perceptible qualitativesignal indicative of state of euhydration, state of dehydration, orsalivary secretion rate based at least in part on such comparison.

In certain embodiments, a hydration state sensing device may provide aquantitative output signal based on results of one salivary test method,and provide a qualitative output signal based on results of one salivarytest method. For example, a device may provide a quantitative outputsignal indicative of salivary secretion rate, and provide a qualitativeoutput signal indicative of analyte concentration (or vice-versa).

One or more user-perceptible output signals representing a quantitativeand/or qualitative values may be generated by one or more signalingelements, such as (but not limited to) a LCD display, a LED array, analphanumeric display, one or more lamps (e.g., LEDs), a sound generatingdevice (e.g., a speaker), and/or a tactile signaling element such as avibration generator. Multiple signaling elements may be provided. Incertain embodiments, a sound generating device provides an output signalin the form of a synthesized voice.

In certain embodiments, a salivary stimulating agent is applied to asubject prior to or concurrent with placement of a liquid collectionelement (or portion thereof) in the subject's mouth, utilizing a deviceand method for sensing salivary secretion rate. In certain embodiments,a salivary stimulating agent may be coated on or otherwise administeredto a user by a liquid collection element. A salivary stimulating agentmay be arranged for gustatory and/or olfactory stimulation of salivaproduction. Examples of gustatory salivary stimulating agents include(but are not limited to) citric acid and sodium chloride. In oneembodiment, a saliva stimulant coating may include citric acid (35-45%),sugarless sour candy (54%-64%) and sodium chloride (1%). Mechanicalstimulation of saliva production (e.g., a mechanical salivarystimulating element) may also be used. In certain embodiments, achewable article such as chewing gum is administered to a user prior toor concurrent with placement of a liquid collection element (or portionthereof) in a subject to mouth, in order to stimulate saliva productionby chewing.

In certain embodiments, a salivary collection device comprising achewable article is administered to a subject, to promote mechanicalstimulation of saliva production (optionally in combination with one ormore gustatory and/or olfactory salivary stimulating agents) andcollection of saliva generated by the subject. Such a chewable articlemay comprise a salivary collection pad or other collection element. Incertain embodiments, both a chewable article and a salivary collectionpad are administered to the subject, whether in a simultaneous orsequential fashion, to stimulate saliva production and collection of thestimulated saliva. After stimulated saliva production and salivacollection is complete, a saliva collection element may be removed fromthe mouth of the subject, optionally subjected to one or more treatmentsteps (e.g., with buffer), and subjected to one or more analytical stepsas described herein.

In certain embodiments, an apparatus for sensing state of euhydration,state of dehydration, or salivary secretion rate of a mammalian subjectincludes a substrate arranged to support or engage a liquid-permeableliquid collection element arranged to transport liquid by wicking, andhaving a predefined liquid holding capacity. The substrate has multipleelectrical contact pairs including a first electrical contact pair and a(downstream) second electrical contact pair. The first electricalcontact pair may be arranged to close a first electrical circuit uponexposure to saliva when the liquid collection element is placed in fluidcommunication with oral mucosa of the mammalian subject, and the secondelectrode pair is arranged to close a second electrical circuit uponexposure to saliva transported though at least a portion of the liquidcollection element. A timing element may be arranged to receive a signalindicative of closure of the first electrical circuit, arranged toreceive a signal indicative of closure of the second electrical circuit,and arranged to generate a first time value indicative of time elapsedbetween the closure of the second electrical circuit and the closure ofthe first electrical circuit. A signaling element may be arranged togenerate an output signal indicative of state of euhydration, state ofdehydration, or salivary secretion rate of the mammalian subject basedat least in part on the first time value. In certain embodiments, one ormore additional downstream electrical contact pairs may be provided, andmigration of saliva to contact these downstream electrical contact pairsmay be used to generate additional (e.g., second, third, fourth, etc.)time values, wherein the output signal may be based at least in part onthe multiple time values, or on one or more signals derived from themultiple time values.

In certain embodiments, an apparatus for sensing a state of euhydration,state of dehydration, or salivary secretion rate of a mammalian subjectincludes a salivary stimulating agent, a liquid collection element,multiple electrodes or sensing elements, a timing element, and asignaling element. The liquid collection element is arranged forplacement in fluid communication with oral mucosa of a user, may beliquid permeable, be arranged to transport liquid by wicking, and have apredefined liquid holding capacity. The salivary stimulating agent isarranged for placement into the mouth prior to or substantiallyconcurrently with establishment of fluid communication between theliquid collection element and oral mucosa. At least one first electrodeor sensing element is arranged to sense a condition indicative ofexposure of a portion of the liquid collection element to oral mucosa,and at least one second electrode or sensing element arranged to sense acondition indicative of movement by saliva through at least a portion ofthe liquid collection element. The timing element may be initiatedresponsive to receipt of a signal from or detection of change of stateof the (at least one) first electrode or sensing element, and generate atime value indicative of elapsed time since said initiation upon receiptof a signal from or detection of a change of state of the (at least one)second electrode or sensing element. The signaling element may generatean output signal indicative of state of euhydration, state ofdehydration, or salivary secretion rate based at least in part on thetime value. Such a device may be supplemented by at least one indicatoror test region arranged to interact with one or more analytes in salivaof the user. An optical reading element may be arranged to generate anelectrical signal correlative of concentration one or more analytes uponoptical interaction with indicator or test region(s). A signalprocessing element may use at least one time value in combination withthe electrical signal correlative of concentration one or more analytesto generate an output signal indicative of the hydration state orsalivary secretion state.

In certain embodiments, a method for sensing hydration state or salivarysecretion rate includes steps such as inserting a salivary stimulatingagent into the mouth of the mammalian subject to stimulate saliva flow;placing at least a portion of a liquid collection element of predefinedliquid holding volumetric capacity in contact with oral mucosa of themammalian subject; detecting a condition indicative of presence ofsaliva on or adjacent to the liquid collection element upon exposure ofthe at least a portion of the liquid collection element to oral mucosaof the mammalian subject, and responsively starting a timer; detecting acondition indicative of movement of saliva through at least a portion ofthe liquid collection element while the at least a portion of the liquidcollection element is exposed to oral mucosa of the mammalian subject,and responsively storing a time value indicative of elapsed time sincethe timer was started; and utilizing the time value to generate anoutput signal indicative of state of euhydration, state of dehydration,or salivary secretion rate of the mammalian subject. A conditionindicative of movement of saliva through the liquid collection elementmay include detecting saturation of at least a portion or the entiretyof the liquid collection element.

In certain embodiments, a first method for sensing a state ofeuhydration, state of dehydration, or salivary secretion rate isutilized, and based on the results of the first method, a second methodsensing a state of euhydration or dehydration is applied may be utilizedto validate the first method. For example, sensing of salivary secretionrate may be utilized first to provide results characterized by highsensitivity, but comparatively low specificity. Thereafter, sensing ofconcentration of at least one analyte in saliva may be utilized, toprovide results of relatively high sensitivity, but comparatively higherspecificity. Utilization of two distinct methods for sensing state ofeuhydration or dehydration provides a very high confidence level ifresults of the different methods are consistent.

In certain embodiments, at least one method for sensing a state ofeuhydration or dehydration as described herein is applied to a useraccording to a first testing step, one or more output values yieldedfrom the first testing step is stored in a memory, then at least onemethod for sensing a state of euhydration or dehydration as describedherein is applied to the same user according to a second testing step,and one or more output value yielded from the first testing step arecompared to one or more stored values. Such steps may be periodicallyrepeated as necessary to assess change in hydration state of the user.

In certain embodiments, a liquid collection element utilized for sensingsalivary secretion rate may be provided in fluid communication with animmunochromatographic lateral flow test strip including at least oneindicator or test region arranged to interact with at least one analytein saliva obtained from the mammalian subject, so that a salivaryanalyte concentration in sensing method may be performed following thesensing of salivary secretion rate utilizing the same saliva sample. Aconjugate pad (e.g., including monoclonal antibodies conjugated to goldnanoparticles) employed by an immunochromatographic assay for sensingsalivary analyte concentration may be arranged between a liquidcollection element and an immunochromatographic test strip.

In certain embodiments, a liquid collection element and animmunochromatographic test strip are arranged in or on a commonsubstrate or housing. In other embodiments, a liquid collection elementis associated with a first substrate or housing, and animmunochromatographic test strip is associated with a second substrateor housing. Following completion of a salivary secretion rate sensingmethod, a liquid collection pad may be treated with a buffer solution,and a buffered saliva composition may be supplied to animmunochromatographic test device. One potential benefit of suchbuffering is to mitigate variability in saliva samples (e.g., viscosity,tonicity, ionic strength, and/or pH) that may otherwise reducereliability of an immunochromatographic assay.

In certain embodiments, an immunochromatographic lateral flow test stripincludes a uniform layer of monoclonal antibodies adapted to bind aselected analyte in saliva. Examples of suitable analytes include (butare not limited to) IgA (e.g., secretory IgA, or SIgA), salivaryalbumin, secretory component, and salivary aldosterone, and while SIgAis mentioned hereafter, it is to be understood that any suitable analytemay be used. An immunochromatographic lateral flow test strip may bedesigned to bind a calibrated quantity of SIgA (e.g., using anti-SIgA)per millimeter of strip length. As saliva enters the strip, the SIgA iscolorized by passing through a conjugate pad containing anti-SIgAconjugated to nano-gold particles which binds to the SIgA, imparting acolor (e.g., pink) to the analyte. When all of the colored SIgA is boundto the strip, the remaining length of the strip remains white. Marks maybe delineated by a cover optionally containing multiple holes thatreveal the strip at various points along its length, with each pointingrepresents a total amount of SIgA per ml of saliva. Calibration marksmay be arranged proximate to openings in the cover to permitquantitative assessment of analyte concentration based upon presence (orabsence) of color in an adjacent window.

In certain embodiments, an immunochromatographic lateral flow test stripincludes a series of antibody (e.g., anti-SIgA) bands arranged asstripes aligned perpendicular to a long dimension of the strip. Eachstripe line has a specific (though not necessarily the same) analyteabsorptive capacity. Thus, substantially the same method as articulatedin the preceding paragraph can be accomplished using a series of stripedbands rather than a uniform layer of antibodies for the selected analyteover the entire strip.

In certain embodiments, an immunochromatographic lateral flow test stripand cover are arranged to provide a positive control region (e.g.,corresponding to a window defined in a cover over the strip) disposeddownstream of a conjugate pad but upstream of one or more indicatorwindows providing quantitative or qualitative indication of hydrationstate. Colorization of such a positive control region (e.g., with pinkcolor) will indicate that a liquid sample is present within the lateralflow test strip, that the conjugate pad is functional, and that thesample contains the analyte (or analytes) of interest. Presence of acolored signal in the positive control region increases confidence inquantitative or qualitative signals generated in downstream testwindows.

In certain embodiments, one or more immunochromatographic lateral flowtest strips or portions thereof within the same apparatus may includedifferent monoclonal antibodies arranged to bind different analytes. Incertain embodiments, an immunochromatographic lateral flow test stripincludes a first group of monoclonal antibodies arranged to interactwith a first analyte selected from IgA, albumin, secretory component,and aldosterone, and a second group of different monoclonal antibodiesarranged to interact with a second analyte selected from IgA, albumin,secretory component, and aldosterone, wherein the second analyte differsfrom the first analyte. Different antibodies arranged to interact withdifferent analytes may be provided in one or more of same test orindicator regions located along a single immunochromatographic lateralflow test strip, may be provided in different test or indicator regionslocated along parallel flow paths in a single immunochromatographiclateral flow test strip, or may be provided in different test orindicator regions located in multiple immunochromatographic lateral flowtest strips arranged in parallel within a single device or system.Different analytes may be colored differently (e.g., blue and yellow)via one or more conjugate pads. Signals based upon a combination ofdifferent analytes bound in the same region may be combined (e.g., blueand yellow combined to make a green color). Immunochromatographiclateral flow test strips arranged to interact with multiple analytes maybe arranged to perform different assay formats, such as a competitivebinding assay format or a sandwich assay format.

In certain embodiments, at least one of oral fluids, intravenous fluids,electrolytes, medication, and medical treatment is administered to auser based on one or more output signals generated by hydration statesensing devices and methods as described herein. In certain embodiments,an output signal from an apparatus as described herein may becommunicated (e.g., via wired or wireless communication) to anadministering element to facilitate automated administration of at leastone of oral fluids, intravenous fluids, electrolytes, medication, andmedical treatment of fluids without human intervention.

In certain embodiments, operation of one or more sensing methods orprocessing of results thereof may be affected by one or more signalsreceived from a user input element. In various embodiments, a user inputelement may be used to store one or more sensed values, to compare oneor more currently sensed values to one or more stored valuescorresponding to previously sensed values, and/or to select a userpopulation of which the user is a member. To the extent that userpopulation status (e.g., age, sex, disease state, medication usage,activity level, or the like) may affect comparison values used toprovide qualitative assessments, user input information may be used toadjust or select appropriate comparison values to as a basis forproviding a qualitative output signal.

Referring to the figures, is a schematic diagram showing interconnectionof various components of a system 100 for sensing a state of euhydrationor dehydration of a subject via saliva of the subject is illustrated inFIG. 1. A liquid collection element and/or interface 101 includesmultiple electrodes or sensors 121, 122 that may be arranged to sense acondition indicative of exposure of the liquid collection element tooral mucosa, and to sense a condition indicative of saturation of thepredefined liquid holding capacity of the liquid collection element.Such electrodes or sensors 121, 122 may therefore be used toautomatically start and stop a timing element (e.g., a timer) togenerate a time value correlative of salivary secretion rate. Theelectrodes or sensors 121, 122 are arranged in electrical communicationwith a processing/control element 170 having an associated battery 171and a memory 172. In certain embodiments, the processing/control element170 comprises a microprocessor arranged to execute a predefinedmachine-readable instruction set. The processing/control element 170 mayprovide timing functionality, or a separate timer (not shown) may beused. A signaling or output element 150, which may be embodied in adisplay, is arranged in electrical communication with theprocessing/control element 170. A reading element 173 such as an opticalreader may be arranged in communication with the processing/controlelement 170. The processing/control element 170 may receive user inputsignals from a user input element 175. A communication element 195, suchas may be embodied in a wired interface (e.g., a plug or socket) and/orwireless interface (e.g., a transmitter or transceiver), may be arrangedto permit communication and signals between the processing/controlelement 170 and at least one terminal or remote communication device196. In this manner, signals indicative of state of euhydration ordehydration of a user may be monitored and logged remotely (e.g., at anurse's station or a sport manager's communication device), and actionsmay be taken responsive to such signals. In certain embodiments, aterminal or remote communication device 196 arranged to receive signalsindicative of state of euhydration or dehydration may be worn by a userwhile participating in an athletic event.

FIG. 2 is a side cross-sectional schematic view of a portion of a salivacollection element 210 arranged in contact with an interface portion 201of a hydration state sensing device according to certain embodiments ofthe present invention. A body structure 231 includes a substrate 230arranged to support the saliva collection element 210, and includes acover portion 232 is pivotally mounted to the body structure 231 with ahinge 232A. A first pair of electrodes 221A, 221B with a gap 223therebetween is arranged proximate to a first end 211 of the salivacollection element 210, and a second electrode or electrode pair 222A isarranged proximate to a second end 212 of the saliva collection element210. A first portion 213 of the saliva collection element 210 proximateto the first end 211 is exposed to receive and absorb saliva when thefirst end 211 is placed into the mouth of a user to contact oral mucosa.A second portion 214 of the saliva collection element 210 proximate tothe second end 212 is covered with the cover element 232. This coveringarrangement ensures that liquid can only reach the second electrode orelectrode pair 222A by lateral flow through the saliva collectionelement 210. The electrodes 221A, 221B, 222A may be formed in or on thesubstrate 230 with suitable electrical traces (not shown) providingelectrical communication with a processing or control element. The firstset of electrodes 221A, 221B may be defined through one or both surfacesof the substrate 230, whereas the second electrode or electrode pair222A is preferably only accessible to liquid by lateral flow through thesaliva collection element 210. The saliva collection element 210 may beadhered or otherwise affixed to the substrate 230. One or more portionsof the substrate 230 proximate to the first portion 213 may defineopenings (not shown) or be liquid permeable to permit saliva to contactthe saliva collection element 210.

FIG. 3 is a side cross-sectional schematic view of a saliva collectionelement 310 having integral electrodes 321A, 321B, 322A, and a backingelement 318 and a covering element 319, with a sandwiched layer portion314 arranged between the backing element 318 and the covering element319, and with an exposed layer portion 313 supported above the backingelement 318. A first pair of electrodes 321A, 321B separated by a gap323 is arranged proximate to a first end 313 of the saliva collectionelement 310, and a second electrode or electrode pair 322A is arrangedproximate to a second end 312 of the saliva collection element 310. Thesaliva collection element 210 may be mechanically supported by asupporting substrate (not shown), or may be retained within a bodystructure (not shown) proximate to the second end 312.

FIG. 4 is a top plan schematic view of a saliva collection element 410having integral electrodes with a guide channel portion 426 arrangedbetween two electrode pairs 421A-421B, 422A-422B. The first electrodepair 421A-421B is separated by a first gap 423, and the second electrodepair 422A-422B is separated by a second gap 424. The guide channelportion 426 includes a channel of reducing width (e.g., roughlytriangular in shape) defined by boundary regions 427 treated withhydrophobic or water-impermeable material such as adhesive, wax, or thelike. The function of the guide channel portion 426 is to preventpremature triggering of an output signal by the second electrode pair422A-422B. That is, such guide channel portion 426 serves to guide afrontal edge of saliva advancing within the saliva collection element410 in order to promote saturation of the saliva collection element 410with saliva before the second electrode pair 422A-422B generates asignal indicating such saturated condition has been attained.

Although various electrode configurations have been shown, it is to beappreciated that any suitable positioning of electrodes relative to asaliva (or liquid) collection element may be employed. Moreover, any ofvarious suitable types of sensors may be utilized instead of or inaddition to such electrodes.

FIG. 5 is a top cross-sectional schematic view of a device 500 forsensing a state of euhydration or dehydration of a subject utilizingsaliva according to certain embodiments of the present invention, withthe device 500 arranged to sense both salivary secretion rate andconcentration of at least one analyte in saliva. The device 500 includesa liquid collection element 510 with a first pair of electrodes521A-521B arranged to detect insertion of a first end 511 of the liquidcollection element 510 into a user's mouth (with insertion of the device500 into a user's mouth being limited by a mouth insertion shield 533),and a second pair of electrodes 522A-522B arranged to detect migration(e.g., wicking) of saliva to a second end 512 of the liquid collectionelement 510 as indicative of a condition of saturation thereof. Thesecond end 512 of the liquid collection element 510 is preferablyarranged within a body structure 531 to ensure that saliva reaches thesecond end 512 only by lateral migration through the liquid collectionelement 510. First and second electrical traces 581, 582 provideelectrical communication between a processing or control element (notshown) associated with the device 500 and the electrode pairs 521A-521B,522A-522B. A signaling element 550 in the form of a display is arrangedto receive time value signals from a timer (not shown) operativelyconnected to the first and second electrode pairs 521A-521B, 522A-522Band to provide a user-perceptible signal quantifying salivary secretionrate (e.g., as an alphanumeric value).

When the salivary secretion rate sensing is complete, the device 500preferably generates a user-perceptible signal (e.g., audible and/orvisible) prompting the user to place the liquid collection device 510(still attached to the device 500) into a tube or other container ofbuffer solution (not shown). The liquid collection element 510 is influid communication with a downstream immunochromatographic lateral flowstrip 540. Buffered saliva flows by wicking through a transition zone534 past the second electrode pair 522A-522B to contact a conjugate pad535 including monoclonal antibodies conjugated to gold nanoparticles,thereby imparting pink color to the analyte. As saliva continues to flowthrough the lateral flow strip 540 in a direction toward a distal end599 of the device 500, the colored analyte is absorbed by the strip 540to impart color to the strip 540. When all of the colored analyte isbound to the strip 540, any remaining length of the strip 540 remainswhite in color. As saliva progresses through the strip 540 toward thedistal end 599 and analyte in the saliva is bound to the strip 540,colorization of the strip may be progressively lighter in color in adirection toward the distal end 599. The higher the concentration oftarget analyte present in the saliva, the greater extent of the strip540 will be colorized. Test or indicator regions 541-545 having aprogressive gradation in color from pink to white following completionof the immunoassay are arranged along the length of the strip 540. Suchtest or indicator regions 541-545 may constitute discrete regions (e.g.,stripes arranged perpendicular to the length of the strip 540) ofmonoclonal antibodies, or may constitute portions of a strip 540uniformly coated with monoclonal antibodies that are exposed via windows(not shown) defined in a cover portion of the body 531. Calibrationmarks are provided adjacent to (i.e., to the right of) the test orindicator regions 541-545, to enable concentration of analyte in thesaliva to be quantified. A third pair of electrodes 548A-548B withassociated electrical traces 588 are arranged at the end of the lateralflow strip 540 to detect presence of saliva as indicative of the end ofthe immunoassay. The device 500 therefore enables quantification of bothsalivary flow rate and salivary analyte concentration, with each beingcorrelative of state of euhydration or dehydration of the user.

FIG. 6 is a top plan schematic view of a second device 600 (similar tothe apparatus of FIG. 5) for sensing a state of euhydration ordehydration of a subject utilizing saliva. The device 600 operates in amanner substantially the same as the device 500, but includes additionalsignaling elements 651-653 arranged along one end 699 proximate to thedisplay 650 to aid in operation of the device 600. The device 600includes a liquid collection element 610 extending into a body structure631 and having an end 611 adapted for insertion in the mouth of a user,with insertion of the device 600 into a user's mouth being limited by amouth insertion shield 633. The body or housing 631, which is preferablyopaque in character, includes a series of window 661-665 permittingviewing of the test or indicator regions 641-645. In operation of thedevice 600, the liquid collection element 610 is placed into the mouthof a user to initiate collection of saliva for sensing of salivarysecretion rate. A first signaling element 651 (e.g., green LED) isactivated to signal contact of the liquid collection element 610 withthe oral mucosa under the user's tongue. When the liquid collectionelement 610 is saturated (filled) with saliva, a second signalingelement 652 (e.g., yellow LED) is activated to signify that salivacollection is complete, and that the liquid collection element 610should be removed from the user's mouth and placed into a buffersolution (not shown). A lateral flow strip internal to the body orhousing 631 is used to perform an immunochromatographic assay to senseconcentration of at least one analyte in the (buffered) saliva,including flow of the buffered saliva past the test or indicator regions641-645 as visible through the windows 661-665. When theimmunochromatographic lateral flow assay is complete, a third signalingelement 653 (e.g., red LED) is activated to signify completion of same.Such signaling elements 651-653 provide user feedback as to operationalstate and prompt the user when one action is completed (and anotheraction should be initiated). It is to be appreciated that non-visualsignaling elements such as audible or tactile signaling elements mayadditionally or alternatively be used.

In certain embodiments, a device for sensing a state of euhydration ordehydration of a subject utilizing saliva may provide one or morequalitative assessments of hydration status. For example, referring toFIG. 7, a device 700 arranged to sense both salivary secretion rate andconcentration of at least one analyte in saliva, to provide aqualitative output signal based on salivary secretion rate (e.g., incomparison to one or more stored or predefined values indicative ofsalivary secretion rate), and to provide a qualitative signal based onanalyte concentration (e.g., in comparison to one or more stored orpredefined values indicative of analyte concentration). The device 700includes a liquid collection element 710 with a first pair of electrodes721A-721B arranged to detect insertion of a first end 711 of the liquidcollection element 710 into a user's mouth (with insertion of the device700 into a user's mouth being limited by a mouth insertion shield 733),and a second pair of electrodes 722A-722B arranged to detect migration(e.g., wicking) of saliva to a second end 712 of the liquid collectionelement 710 as indicative of a condition of saturation thereof. Thesecond end 712 of the liquid collection element 710 is preferablyarranged within a body structure 731 to ensure that saliva reaches thesecond end 712 only by lateral migration through the liquid collectionelement 710. First and second electrical traces 781, 782 provideelectrical communication between a processing or control element (notshown) associated with the device 700 and the electrode pairs 721A-721B,722A-722B. A signaling element 750 in the form of a display is arrangedto receive time value signals from a timer (not shown) operativelyconnected to the first and second electrode pairs 721A-721B, 722A-722Band to provide a user-perceptible qualitative signal (e.g., audibleand/or visible signal) indicating whether salivary secretion rate isconsistent with a specific hydration state, such as euhydration ordehydration. In certain embodiments, a visible signal is provided by adisplay element (e.g., display 750) arranged to display a “+” symbol ifthe user's salivary flow rate is consistent with a state of dehydration,and a “−” symbol if the user's salivary flow rate is consistent with astate of euhydration.

When the salivary secretion rate sensing is complete, the device 700preferably generates a user-perceptible signal (e.g., audible and/orvisible) prompting the user to place the liquid collection device 710(still attached to the device 700) into a tube or other container ofbuffer solution (not shown). The liquid collection element 710 is influid communication with a downstream immunochromatographic lateral flowstrip 740 arranged within a body structure 731 of the device 700.Buffered saliva flows by wicking through a transition zone 734 past thesecond electrode pair 722A-722B to contact a conjugate pad 735 includingmonoclonal antibodies conjugated to gold nanoparticles, therebyimparting pink color to the analyte. As saliva continues to flow throughthe lateral flow strip 740 in a direction toward a distal end 799 of thedevice 700, the colored analyte is absorbed by the strip 740 to impartcolor to the strip 740. A positive control region 741 (e.g.,corresponding to a window defined in a cover portion of the bodystructure 731) including monoclonal antibodies arranged to bind thecolored analyte is arranged downstream of the conjugate pad 735.Colorization of the positive control region 741 (e.g., with pink color)will indicate that a liquid sample is present within the lateral flowtest strip, that the conjugate pad is functional, and that the samplecontains the analyte (or analytes) of interest. Downstream of thepositive control region 741 is a test region 742 arranged to bindcolored analyte in the buffered saliva, if such analyte is present atthe position of the test region 742. That is, between the control region741 and the test region 742 are additional monoclonal antibodiesarranged to bind the colored analyte, and depending on the initialconcentration of the analyte in the saliva, there may or may not besufficient analyte remaining in the sample to colorize the test region742. Presence of a color (e.g., pink) in the test region 742 indicatesthat a relatively high concentration of analyte was originally presentin the saliva sample collected by the liquid collection element 710,whereas lack of non-white color in the test region 742 indicates that arelative low concentration of analyte was originally presented in thesaliva sample. The test region 742 therefore provides a qualitativesignal correlative of state of euhydration or dehydration. Variousparameters such as spacing between the control region 741 and the testregion 742; amount of monoclonal antibody present at the control region,at the test region 742, and between the control region 741 and the testregion 742; concentration or amount of coloring agent in the conjugatepad 735; and so on may be adjusted to provide an appropriate signaldiscrimination level at the control region 742. Each of the positivecontrol region 741 and the test region 742 may have an associated window(not shown) defined in the body structure 731 to reveal the regions 741,742 for visual inspection thereof without revealing a portion of thetest strip 740 disposed therebetween. A third pair of electrodes748A-748B with associated electrical traces 788 are arranged at the endof the lateral flow strip 740 to detect presence of saliva as indicativeof the end of the immunoassay. The device 700 therefore providesqualitative signals for each of salivary flow rate and salivary analyteconcentration, with each being correlative of state of euhydration ordehydration of the user. It is to be appreciated that the device 700 maybe modified to provide quantitative signals for salivary secretion rate,and/or subjected to further analysis (e.g., using an optical readerarranged to interact with the test region 742 (or the test region 742 incombination with the control region 741) to provide quantitative signalsfor analyte concentration.

FIG. 8 is a top plan schematic view of another device 800 (similar tothe apparatus of FIG. 7) for providing qualitative signals indicative ofa state of euhydration or dehydration of a subject utilizing saliva, bysensing salivary secretion rate and concentration of at least oneanalyte in saliva. The device 800 operates in a manner substantially thesame as the previously-described device 700, but includes additionalsignaling elements 851-853 arranged along a distal end 899 proximate tothe display 850 to aid in operation of the device 800. The device 800includes a liquid collection element 810 extending into a body structure831 and having an end 811 adapted for insertion in the mouth of a user,with insertion of the device 800 into a user's mouth being limited by amouth insertion shield 833. The body or housing 831, which is preferablyopaque in character, includes a first window 861 arranged to permitviewing of an immunochromatographic positive control region 841, andincludes a second window 862 arranged to permit viewing of animmunochromatographic test or indicator region 862. In operation of thedevice 800, the liquid collection element 810 is placed into the mouthof a user to initiate collection of saliva for sensing of salivarysecretion rate. A first signaling element 851 (e.g., green LED) isactivated to signal contact of the liquid collection element 810 withthe oral mucosa under the user's tongue. When the liquid collectionelement 810 is saturated (filled) with saliva, a second signalingelement 852 (e.g., yellow LED) is activated to signify that salivacollection is complete, and that the liquid collection element 810should be removed from the user's mouth and placed into a buffersolution (not shown). An lateral flow strip internal to the body orhousing 831 is used to perform an immunochromatographic assay to senseconcentration of at least one analyte in the (buffered) saliva,including flow of the saliva past the control region 841 (visiblethrough a first window 861 defined in the body or housing 831) and pastthe test or indicator region 842 (visible through a second window 862defined in the body or housing 831). Presence of a non-white colored(e.g., pink) signal in the test or indicator region 842 indicates highconcentration of analyte (e.g., IgA, albumin, secretory component, oraldosterone) in the saliva, indicating that the user is in a dehydratedstate. When the immunochromatographic lateral flow assay is complete, athird signaling element 853 (e.g., red LED) is activated to signifycompletion of same. Another signaling element 854 may be provided forauditory signaling corresponding to any of the foregoing conditions,and/or to provide visible signaling of further information such asdevice state, battery status, etc. Such signaling elements 851-854provide user feedback as to operational state and prompt the user whenone action is completed (and another action should be initiated).

In certain embodiments, a device for sensing a state of euhydration ordehydration of a subject utilizing saliva may include a sampling portionthat is removably insertable into a monitoring portion for use incollecting and analyzing saliva.

FIGS. 9A-9B illustrate a sampling portion 900A and a monitoring portion900B of an apparatus 900 for sensing a state of euhydration ordehydration utilizing saliva of a user. FIG. 9A illustrates the samplingportion 900A arranged proximate to a tube 908 containing buffer solution909. The sampling portion 900A includes a liquid collection element 910arranged along a proximal end 911, and a body or housing 934 arranged toretain an opposite end of the liquid collection element 910. Thesampling portion 900A further includes a mouth insertion shield 933arranged to limit insertion of the sampling portion 900A into a user'smouth, and an immunochromatographic lateral flow strip 940 arrangeddownstream of the liquid collection element 910. The sampling portion900A is designed as a single (disposable) use element, with a distal end949 and lateral flow strip 940 of the sampling portion 900A beingarranged for insertion through an opening 967 (at a first end 998 of themonitoring portion 900B) into a slot or recess 968 defined in amonitoring portion 900B, as shown in FIG. 9B.

The monitoring portion 900B is designed to be sequentially reused withdifferent disposable sampling portions 900A. The monitoring portion 900Bincludes a signaling element 950 in the form of a display arranged toreceive time value signals from a timer (not shown), and additionalsignaling elements 951-954, such as may comprise LEDs and/or audibleoutput elements. Electrodes and/or sensors (not shown) arranged in, on,or adjacent to the sampling portion are in electrical communication witha processing/control element (not shown) of the monitoring portion 900Bto sense (a) a condition indicative of insertion of the liquidcollection element 910 into the mouth of a user in contact with oralmucosa, (b) a condition indicative of saturation of the liquidcollection element 910, and (c) a condition indicative of salivareaching a distal end of the lateral flow strip 940 (at or near thedistal end 949 of the sampling portion 900). The monitoring portion 900Bfurther includes elements 961, 962 which may comprise windows or opticalreading elements arranged for interaction with the immunochromatographiclateral flow strip 940. A first element 961 may be arranged proximate toa positive control region of the strip 940, and a second element 962 maybe arranged proximate to a test or indication region of the strip 940.

In operation, the distal end 949 and lateral flow strip 940 of thesampling portion are inserted through an opening 967 at a first end 998of the monitoring portion 900B into a recess or slot 968 definedtherein, to facilitate electrical and/or sensory communication betweenthe sampling portion 900A and the monitoring portion 900B. With thesampling portion 900A and the monitoring portion 900B so coupled, theliquid collection element 910 along a first end 911 of the samplingportion 900A is inserted into the mouth of a user to contact oral mucosa(e.g., under the user's tongue). One or more first electrodes and/orsensors associated with the liquid collection element 910 senseinitiation of absorption of saliva by the liquid collection element 910and one or more second electrodes and/or sensors (e.g., arranged withina body or housing 934 of the sampling portion 900A) sense a conditionindicating that the liquid collection element 910 is saturated (e.g.,filled to predefined volumetric capacity) with saliva. A first signalingelement 951 may signal initiation of absorption of saliva by the liquidcollection element 910, and a second signaling element 912 may signalsaturation of the liquid collection element 910. A time valuecorresponding to the duration required to saturate the liquid collectionelement 910 may be used to determine salivary secretion rate, and acorresponding quantitative value or qualitative determination may beoutput by the display 950. After the salivary secretion rate sensing iscomplete, the user may be prompted (e.g., by the second signalingelement 952 and/or an auditory tone) to place the liquid collectionelement 910 along the first end 911 into a buffer solution for treatmentof saliva within liquid collection element 910. In certain embodiments,the sampling portion 900B may be retained within the monitoring portion900B during the buffer treatment step; alternatively, the samplingportion 900A may be removed from the monitoring portion 900B during suchbuffer treatment (such as depicted in FIG. 9A) and then reinserted intothe monitoring portion 900B for interpreting or reading results of animmunochromatographic assay performed with the lateral flow strip 940 todetermine concentration of at least one analyte in saliva collected fromthe user. In certain embodiments, the monitoring portion 900B includeselements 961, 962 in the form of windows arranged to permit viewing of apositive control region and a test or indication region, respectively,of the lateral flow strip 940. In other embodiments, one or bothelements 961, 962 of the monitoring portion 900B embodying at least oneoptical readers to assess presence of color at selected portions (e.g.,a positive control region and a test or indication region) of thelateral flow strip 940. If at least one element 961, 962 comprises anoptical reader, then output of such a reader may be displayed (e.g., inquantitative or qualitative fashion) using the display element 950.Results of the salivary secretion rate sensing and the salivary analyteconcentration sensing may be stored and/or compared to one another, andresults of such comparison may be displayed to the user using thedisplay element 950. The device 900 resulting from the combination ofthe sampling portion 900A and the monitoring potion 900B thereforeenables consideration of both salivary secretion rate sensing andsalivary analyte concentration sensing to determine state of euhydrationor dehydration of a user.

In certain embodiments, separate sampling and monitoring portions of ahydration state sensing apparatus may be connected via an electricalcable during a salivary secretion rate sensing step, and the samplingportion may be inserted into the monitoring portion for reading resultsof a subsequent immunochromatographic assay step for determiningconcentration of at least one analyte in the saliva. Referring to FIG.10, a hydration state sensing apparatus 1000 includes a sampling portion1000A and a monitoring portion 1000B connected via an electricalcommunication cable 1058 having associated interface plugs or connectors1057, 1059. The sampling portion 1000A is intended for disposableone-time use, whereas the monitoring portion 1000B is intended to bere-used with different sampling portions 1000A. A processing/controlelement, battery, and timing element (not shown) associated with themonitoring portion 1000B may be provided in electrical communicationwith electrodes and/or sensors (not shown) of the sampling portion 1000Avia the electrical interface cable 1058. The sampling portion 1000Aincludes a liquid collection element 1010 arranged along a proximal end1011, and a body or housing 1034 arranged to retain an opposite end ofthe liquid collection element 1010. The sampling portion 1000A furtherincludes a mouth insertion shield 1033 and an immunochromatographiclateral flow strip 1040 arranged downstream of the liquid collectionelement 1010. In one embodiment, the mouth insertion shield is movable,since the appropriate length of insertion of a portion of a samplingportion may depend on oral cavity size of the user. An interface plug orconnector 1057 is arranged proximate to a distal end 1049 of thesampling portion 1000A. The monitoring portion includes first end 1098and a second end 1099. The monitoring portion 1000B includes a signalingelement 1050 which may comprise a display, and additional signalingelements 1051-1054 which may comprises visual or auditory signalingelements. The monitoring portion 1000B includes an opening 1067 arrangedat a first end 1098 and arranged to receive the distal end 1049 of thesampling portion 1000A for insertion into a slot or recess 1068 definedin the monitoring portion 1000B. In certain embodiments, the monitoringportion 1000B includes elements 1061, 1062 in the form of windowsarranged to permit viewing of a positive control region and a test orindication region, respectively, of the lateral flow strip 1040. Inother embodiments, one or both elements 1061, 1062 of the monitoringportion 1000B embodying at least one optical readers to assess presenceof color at selected portions (e.g., a positive control region and atest or indication region) of the lateral flow strip 1040.

In operation, the sampling portion 1000A and the monitoring portion1000B are initially coupled via the electrical communication cable 1058and associated plugs or connectors 1058-1059. The liquid collectionelement 1010 along a first end 1011 of the sampling portion 1000A isinserted into the mouth of a user to contact oral mucosa (e.g., underthe user's tongue). One or more first electrodes and/or sensorsassociated with the liquid collection element 1010 sense initiation ofabsorption of saliva by the liquid collection element 1010 and one ormore second electrodes and/or sensors (e.g., arranged within a body orhousing 1034 of the sampling portion 1000A) sense a condition indicatingthat the liquid collection element 1010 is saturated (e.g., filled topredefined volumetric capacity) with saliva. A first signaling element1051 may signal initiation of absorption of saliva by the liquidcollection element 1010, and a second signaling element 1012 may signalsaturation of the liquid collection element 1010. A time valuecorresponding to the duration required to saturate the liquid collectionelement 1010 may be used to determine salivary secretion rate, and acorresponding quantitative value or qualitative determination may beoutput by the display 1050. After the salivary secretion rate sensing iscomplete, the user may be prompted (e.g., by the second signalingelement 1052 and/or an auditory tone) to place the liquid collectionelement 1010 along the first end 1011 into a buffer solution (not shown)for treatment of saliva within liquid collection element 1010.Thereafter, the sampling portion 1000A may be disconnected from thecable 1058 by removal of the plug or connector 1057, and the distal end1049 of the sampling portion may be inserted via the opening 1067 intothe slot or recess 1068 of the monitoring portion 1000B forinterpretation or reading of the results of the immunochromatographicassay performed in the lateral flow strip 1040 as aided by the elements1061, 1062 (e.g., in the form of windows or optical reading elements).The apparatus 1000 therefore provides both salivary secretion ratesensing and salivary analyte concentration sensing utility, to permitassessment of state of euhydration or dehydration of a user.

In certain embodiments, a system for sensing salivary secretion rate andsalivary analyte concentration may utilize a first apparatus forsalivary secretion rate sensing and a second apparatus for salivaryanalyte concentration sensing. FIG. 11A illustrates a salivary secretionrate sensing apparatus 1000 of a system for sensing a state ofeuhydration or dehydration of user, and FIG. 11B illustrates a salivaryanalyte concentration sensing apparatus 1195 of such system. Thesalivary secretion rate sensing apparatus 1100 includes a samplingportion 1100A and a monitoring portion 1100B connected via an electricalcommunication cable 1158 and associated plugs or connectors 1157, 1159.The sampling portion 1100 includes a liquid collection element 1110arranged along a proximal end 1111, and a body or housing 1034 arrangedto retain an opposite end of the liquid collection element 1010, with antubular extension 1132 extending from the body or housing 1034 tocontact one plug or connector 1157. A processing/control element,battery, and timing element (not shown) associated with the monitoringportion 1100B may be provided in electrical communication withelectrodes and/or sensors (not shown) of the sampling portion 1100A viathe electrical interface cable 1158. The monitoring portion 1100Bfurther includes a display 1150 and first and second signaling elements1151, 1152.

The salivary analyte concentration sensing apparatus 1195 includes abody or housing 1196 with a liquid collection element 1192 arranged atone end 1191, a conjugate pad 1135 downstream of the liquid collectionelement 1192, and an immunochromatographic lateral flow strip 1140downstream of the conjugate pad 1135. A positive control region 1141having an associated first window 1140 is provided downstream of theconjugate pad 1135, and a test or indication region 1142 having anassociated second window 1162 downstream of the positive control region1141 as liquid flows within the strip 1140 toward a distal end 1199 ofthe apparatus 1195.

In operation, the liquid collection element 1110 of the sampling portion1100A of the salivary secretion rate apparatus 1000 is inserted into themouth of a user, and a timer (e.g., contained within the monitoringportion 11008) is automatically started upon detection by at least onefirst sensor or electrode associated with the liquid collection element1110. When the liquid collection element 1110 is saturated with saliva,at least one first sensor or electrode associated with the liquidcollection element 1110 senses such condition and causes the timer tostop. Salivary secretion rate may be determined by dividing theresulting time value from the predefined volumetric capacity of theliquid collection element 1110. Signaling elements 1151, 1152 may signalstarting and stopping of liquid collection, and either quantitative orqualitative output signals based on salivary secretion rate may beoutput via the display 1150. Thereafter, concentration of at least oneanalyte in the user's saliva may be sensed via the salivary analyteconcentration sensing apparatus 1195.

In certain embodiments, the liquid collection element 1110 of thesampling portion is placed into, or otherwise washed or exuded (e.g., bysqueezing or wringing) into a buffer, such as buffer 1109 in tube 1108.In other embodiments, the liquid collection element 1110 of the samplingportion 1100A is removed and placed into the housing 1196 of thesalivary analyte concentration sensing apparatus 1195 to serve as theliquid collection element 1191 thereof, and then treated with buffersolution 1109. In other embodiments, the liquid collection element 1110of the sampling portion 1110 is placed into contact with the liquidcollection element 1192 of the of the salivary analyte concentrationsensing apparatus 1195 (e.g., and optionally pressed) to transfer salivainto to the liquid collection element 1192, followed by treatment withbuffer solution 1109. In other embodiments, a dedicated liquidcollection element 1192 associated with the salivary analyteconcentration sensing apparatus 1195 is placed into the user's mouth togather a saliva sample, and the saliva-containing liquid collectionelement 1192 may be treated with buffer solution 1109,

After saliva is present in the liquid collection element 1191 andbuffered, the buffered saliva travels by wicking through a conjugate pad1135 and into the immunochromatographic lateral flow strip, past thepositive control region 1141 and the test or indication region 1142. Asindicated previously, presence of color in the test or indication region1142 indicates high salivary analyte concentration, which may indicate astate of dehydration of the user.

In certain embodiments, saliva production of a mammalian subject isstimulated, collected, and analyzed, such as to determine presenceand/or concentration of at least one analyte in the collected saliva, asmay be used to sense a state of euhydration or dehydration of thesubject. In certain embodiments, presence and/or concentration ofmultiple analytes may be sensed, and signals correlative of presenceand/or concentration of different analytes may be compared to provide anindication of state of euhydration or dehydration. Any one or moreanalytes in saliva may be used. In certain embodiments, at least oneanalyte subject to detection may include any of IgA, albumin, secretorycomponent, and aldosterone.

Stimulation of production of saliva may include administering agustatory salivary stimulating agent to the subject, administering anolfactory salivary stimulating agent to the subject, and/or use of amechanical salivary stimulating agent (e.g. a chewable article) by thesubject. In certain embodiments, multiple salivary stimulating means maybe utilized in simultaneous or sequential fashion. Stimulated saliva maybe collected by any suitable saliva collection element. In certainembodiments, a saliva collection element is inserted into the mouth ofthe subject to contact oral mucosa. Collected saliva may be treatedprior to the performance of one or more analytical steps utilizing atleast a portion of the saliva. Such treatment may include treatment withat least one buffer (e.g., buffer solution, such as may mitigatevariability in characteristics such as viscosity, tonicity, ionicstrength, and/or pH of raw saliva).

Sensing presence and/or concentration of at least one analyte in thecollected saliva may be performed with any suitable analytical device.In certain embodiments, such analysis is performed with animmunochromatographic lateral flow test strip. In certain embodiments,an optical property of at least one indicator or test region of ananalytical device containing at least a portion of the collected salivamay be analyzed, such as with an optical reader. In various embodiments,an analyte detection signal comprise a user-perceptible qualitativeand/or quantitative signal. In certain embodiments, an analyte detectionsignal may be compared to at least one predetermined reference valueand/or threshold value (with such values optionally being correlated to,or corrected for, one or more attributes of the user, such as age,health condition, drug intake, fluid intake, and so on), with suchcomparison being used to assess state of euhydration or dehydration ofthe mammalian subject. At least one of oral fluids, intravenous fluids,electrolytes, medication, and medical treatment may be administered to amammalian subject based on an analyte detection signal.

In certain embodiments, analysis of presence and/or concentration of atleast one analyte in collected saliva produced with the aid of salivaproduction stimulation means is validated with sensing of salivaproduction rate as disclosed previously herein. For example, an analytepresence and/or concentration analysis may be preceded or followed bysteps including placing at least a portion of a liquid collectionelement of predefined liquid holding volumetric capacity in the mouth ofthe mammalian subject and starting a timer substantially simultaneouslywith exposure of the at least a portion of the liquid collection elementto oral mucosa of the mammalian subject, and sensing a conditionindicative of saturation of the predefined liquid holding capacity ofthe liquid collection element while the at least a portion of the liquidcollection element is exposed to oral mucosa of the mammalian subject,and storing a time value indicative of elapsed time since the timer wasstarted. An analyte detection value may be used in combination with atime value obtained from the foregoing process to assess state ofeuhydration or dehydration of a mammalian subject.

FIG. 15 provides a flowchart of various steps that may be employed inanalyzing presence and/or concentration of at least one analyte incollected saliva produced with the aid of saliva production stimulationmeans. Block 1502 involves the step of stimulating production of saliva.As indicated previously, such stimulation may include administering agustatory salivary stimulating agent to the subject, administering anolfactory salivary stimulating agent to the subject, and/or use of amechanical salivary stimulating agent (e.g. a chewable article) by thesubject. Block 1504 involves collection of stimulated saliva. Anysuitable saliva collection element may be used, including but notlimited to a saliva collection element arranged for placement in contactwith oral mucosa of a mammalian subject. Such saliva collection forpurposes of analyte detection may simultaneously be used for sensing ofsaliva production rate. Block 1506 involves analysis of presence and/orconcentration of one or more analytes in the collected saliva. Anysuitable analytical means as disclosed herein or otherwise known in theart may be used. Block 1508 involves comparison of sensed analyteconcentration(s) or analyte presence to one or more previously sensedvalues or signals. Steps recited in (optional) block 1510 may beperformed responsive to steps performed in block 1506 and/or block 1508,and involve storage of data generated by the sensing and/or comparisonsteps, or processed data derived therefrom. Stored values may be used todetect trends, and also used to generate alarms and/or reports. Stepsrecited in (optional) block 1512 may be performed responsive to stepsperformed in blocks 1508 or 1510, and involve performance of validationand/or follow-up tests. A validation test may involve use of a differentanalyte, different analytical technique, and/or different testmethodology in comparison to an initial test. For example, an initialtest involving steps recited in blocks 1502-1508 may include use of animmunochromatographic test strip to detect concentration of one or moreanalytes in stimulated saliva. A follow-up test may involve use ofsubstantially the same test at a different point in time. A validationtest may involve detection of concentration of one or more differentanalytes, and/or may involve detection of stimulated saliva productionrate as disclosed previously herein. One skilled in the art with thebenefit of the present disclosure will appreciate that any suitabletypes and/or number of tests may be performed over a selected timeperiod.

FIG. 16 is a top plan view of a sampling portion 1600A of an apparatusfor sensing hydration state or salivary secretion rate of a mammaliansubject, the sampling portion 1600A including a liquid collectionelement 1610 arranged over a portion of a substrate 1630 having foursequentially arranged electrical contact pairs 1621A-1621D for sensingpresence of saliva. Each electrical contact pair 1621A-1621D includestwo contacts separated by a gap 1622A-1622D. The substrate 1630, whichhas a first end 1631-1 and a second end 1631-2, comprises a circuitboard (e.g., FR4 material) with conductive electrical traces 1635arranged on surfaces thereof. A protruding portion 1613 of the liquidcollection element 1610 extends beyond the first end 1631-1 of thesubstrate 1630. Such portion 1613 may protrude approximately 5-10 mmbeyond a substrate or housing. At least some electrical traces 1635 arein communication with interface contacts 1638 arranged for electricalconnection to a monitoring portion of such an apparatus (e.g., such asmonitoring portions shown in FIGS. 18-19). Although the substrate 1630is shown as having exposed surfaces, in certain embodiments at least aportion of the substrate may be encased in a housing (not shown).

FIG. 17 is a top plan view of a portion of a sampling portion 1700A ofanother apparatus for sensing hydration state or salivary secretion rateof a mammalian subject, the sampling portion 1700A including a liquidcollection element 1710 with a portion arranged on a substrate within ahousing 1740, and with a protruding portion 1713 of the liquidcollection element 1710 extending beyond a first end 1731-1 of thehousing 1740. The housing 1740 includes a lengthwise ruler or numericscale 1737 arranged to permit measurement of length of insertion of thehousing 1740 into a mouth of a user and/or to permit visual observationof an extent of migration of saliva (although as shown in FIG. 17, theruler or numeric scale 1737 extends well beyond the liquid collectionelement 1710. The ruler or scale 1737 may be desired since the desiredlength of insertion of a collection device may depend on the oral cavitysize. Along a second end 1731-2 of the housing a socket 1739 is providedfor receiving an interface cable for connecting to a monitoring portionof such an apparatus (e.g., such as monitoring portions shown in FIGS.18-19). Although not shown, it is to be understood that the multipleelectrical contact pairs or other sensing elements may be arranged on asubstrate within the housing 1740 proximate to the liquid collectionelement 1710.

FIG. 18 illustrates a monitoring portion 1800B for use with a samplingportion as illustrated in FIG. 16 or FIG. 17. The monitoring portion1800B includes an alphanumeric display 1850 such as may be used tooutput quantitative and/or qualitative information, and multiple otherindicators 1851-1852 arranged to generate user-perceptible signals. Thedisplay 1850 and/or indicators 1851-1852 may be used to output signalsindicative of operating status and/or test results.

FIG. 19 illustrates a monitoring portion 1900B for use with a samplingportion as illustrated in FIG. 16 or FIG. 17. The monitoring portion1900B includes an alphanumeric display 1950 such as may be used tooutput quantitative and/or qualitative information, and multiple otherindicators 1951-1953 arranged to generate user-perceptible signals. Themonitoring portion 1900B further includes an interface cable 1958arranged for coupling (e.g., in removable fashion) with a samplingportion.

FIGS. 20A-20C illustrate a sampling portion 2000A and a monitoringportion 2000B of an apparatus. The sampling portion 2000A includes asubstrate 2030, a liquid collection element 2010 with a protrudingportion 2013 extending beyond an end of the substrate 2030, electricaltraces 2035-2036 provided on the substrate, and an interface connector2038 arranged for removable connection to the monitoring portion 2000B.The monitoring portion 2000B includes a circuit board 2080, analphanumeric display 2050, and processor 2090, and an interface socket2059. As shown in FIG. 20C, the sampling portion 2000A may be coupled tothe monitoring portion 2000B by way of the connector 2038 and the socket2059. Other means of connecting the sampling portion 2000A and themonitoring portion 2000B could be employed, as disclosed previouslyherein.

FIGS. 21A-23B provide results of in vitro tests utilizing samplingportions according to FIG. 16 with liquid collection elements of threedifferent compositions. In each instance a portion of the liquidcollection element was placed in contact with a puddle of salivaarranged on a surface, and time for saliva to migrate from oneelectrical contact pair (or electrode) to the next (i.e., withelectrical contact pair 1621A represented as “A”, electrical contactpair 1621B represented as “B,” and so on).

FIG. 21A is a table summarizing results of five salivary secretion ratesensing tests utilizing a sampling portion with a X5169 collection padand four sequentially arranged electrical contact pairs A to D. FIG. 21Bis a line chart representing time for migration of saliva betweenrespective electrical contact pairs of the salivary secretion ratesensing tests summarized in FIG. 21A, superimposed over a bar chartrepresenting average migration times.

FIG. 22A is a table summarizing results of five salivary secretion ratesensing tests utilizing a sampling portion with a D4607 parallelcollection pad and four sequentially arranged electrical contact pairs Ato D. FIG. 22B is a line chart representing time for migration of salivabetween respective electrical contact pairs of the salivary secretionrate sensing tests summarized in FIG. 22A, superimposed over a bar chartrepresenting average migration times.

FIG. 23A is a table summarizing results of four salivary secretion ratesensing tests utilizing a sampling portion with a D4607 perpendicularcollection pad and four sequentially arranged electrical contact pairs Ato D. FIG. 23B is a line chart representing time for migration of salivabetween respective electrical contact pairs of the salivary secretionrate sensing tests summarized in FIG. 23A, superimposed over a bar chartrepresenting average migration times.

As shown in FIGS. 21B-23B, salivary migration time between the third andfourth electrode pair was slower than salivary migration time betweenthe second and third electrode pair in each instance, despite thesequentially arranged electrode pairs being equidistantly spaced fromone to the next.

FIG. 24A depicts a sampling portion 2400A of an apparatus for sensinghydration state or salivary secretion rate of a mammalian subjectsimilar to the sampling portion illustrated in FIGS. 20A-20C, but withaddition of two (circled) colored polymeric strips or loops 2419A-2419Bas barriers or shielding elements extending over a protruding portion2413 of the liquid collection element 2410. The liquid collectionelement 2410 is in the form of a D4607 perpendicular collection pad, andis arranged over four sequentially arranged electrical contact pairs Ato D (as referenced in FIGS. 24B-24C). The liquid collection element2410 is supported by a substrate 2430 having electrical traces 2435 andan electrical interface connector 2438. The barrier elements2419A-2419B, which are spaced apart to expose portions of the liquidcollection element therebetween, are generally liquid impermeable andare arranged to limit a tendency of an absorptive surface or portion ofthe liquid collection element from being restricted or blocked tofurther liquid flow (e.g., blocking by soft tissue below the tonguethereby sealing or restricting the liquid inlet within a subject'smouth). Presence of the barriers 2419A-2419B thereby prevents salivaryflow restriction or stoppage.

FIG. 24B is a table providing results of three in vivo stimulatedsalivary secretion rate sensing tests utilizing the sampling portion ofFIG. 24A. Saliva production was stimulated to rubbing 5 mg of powderedstimulant (55% citric acid, 45% sour candy) over the subject's tonguefor 2 seconds. Twenty minutes elapsed between collections. FIG. 24C is aline chart representing time for migration of saliva between respectiveelectrodes of the salivary secretion rate sensing tests summarized inFIG. 24B, superimposed over a bar chart representing average migrationtimes. As shown in FIG. 24C, salivary migration time between the thirdand fourth electrode pair was closer to the salivary migration timebetween the second and third electrode pair than was the case in FIGS.21B-23B.

FIG. 25A depicts a sampling portion 2500A of an apparatus for sensinghydration state or salivary secretion rate of a mammalian subjectsimilar to the sampling portion illustrated in FIGS. 20A-20C, but withaddition of a (circled) barrier or shielding element 2525 including twonotches 2529A, 2529B defined therein and arrangeable over a protrudingportion of a liquid collection element (not shown). The barrier orshielding element 2525 may be arranged to prevent blocking by softtissue below the tongue thereby sealing or restricting the liquid inletwithin a subject's mouth. A liquid collection element (not shown) may bearranged over four sequentially arranged electrical contact pairs(referenced as electrodes A to D in FIGS. 25B-25C). Such a liquidcollection element may be supported by a substrate 2530 havingelectrical traces 2535 and an electrical interface connector 2538. Thebarrier or shielding element 2525 is generally liquid impermeable (e.g.,constructed of polymeric material) and is arranged to limit a tendencyof an absorptive surface or portion of the liquid collection elementfrom being restricted or blocked to further liquid flow, therebypreventing salivary flow restriction or stoppage.

FIG. 25B is a table providing results of three in vivo stimulatedsalivary secretion rate sensing tests utilizing the sampling portion ofFIG. 25A. Saliva production was stimulated to rubbing 5 mg of powderedstimulant (55% citric acid, 45% sour candy) over the subject's tonguefor 2 seconds. Twenty minutes elapsed between collections. FIG. 25C is aline chart representing time for migration of saliva between respectiveelectrodes of the salivary secretion rate sensing tests summarized inFIG. 25B, superimposed over a bar chart representing average migrationtimes.

While the invention has been has been described herein in reference tospecific aspects, features and illustrative embodiments of theinvention, it will be appreciated that the utility of the invention isnot thus limited, but rather extends to and encompasses numerous othervariations, modifications and alternative embodiments, as will suggestthemselves to those of ordinary skill in the field of the presentinvention, based on the disclosure herein. Correspondingly, theinvention as hereinafter claimed is intended to be broadly construed andinterpreted, as including all such variations, modifications andalternative embodiments, within its spirit and scope.

1. An apparatus for sensing a state of euhydration, state ofdehydration, or salivary secretion rate of a mammalian subject, theapparatus comprising: a liquid collection element arranged for placementin fluid communication with oral mucosa of a mammalian subject, theliquid collection element being liquid-permeable, being arranged totransport liquid by wicking, and having a predefined liquid holdingcapacity; a substrate arranged to support or engage the liquidcollection element, with the substrate having arranged thereon aplurality of electrical contact pairs including a first electricalcontact pair and a second electrical contact pair arranged downstream ofthe first electrical contact pair, wherein the first electrical contactpair is arranged to close a first electrical circuit upon exposure tosaliva when the liquid collection element is placed in fluidcommunication with oral mucosa of the mammalian subject, and the secondelectrical contact pair is arranged to close a second electrical circuitupon exposure to saliva transported though at least a portion of theliquid collection element; a timing element arranged to receive a signalindicative of closure of the first electrical circuit, arranged toreceive a signal indicative of closure of the second electrical circuit,and arranged to generate a first time value indicative of time elapsedbetween the closure of the second electrical circuit and the closure ofthe first electrical circuit; and a signaling element arranged togenerate an output signal indicative of state of euhydration, state ofdehydration, or salivary secretion rate of the mammalian subject basedat least in part on the first time value.
 2. An apparatus according toclaim 1, wherein: the plurality of electrical contact pairs includesthird electrical contact pair arranged downstream of the secondelectrical contact pair, wherein the third electrical contact pair isarranged to close a third electrical circuit upon exposure to salivatransported by wicking though at least a portion of the liquidcollection element; the timing element is arranged to receive a signalindicative of closure of the third electrical circuit, and is arrangedto generate a second time value indicative of time elapsed between theclosure of the third electrical circuit and the closure of one of (a)the first electrical circuit and (b) the second electrical circuit; andthe signaling element is arranged to generate an output signalindicative of state of euhydration, state of dehydration, or salivarysecretion rate of the mammalian subject based at least in part on thefirst time value and the second time value.
 3. An apparatus according toclaim 2, wherein: the plurality of electrical contact pairs includesfourth electrical contact pair arranged downstream of the thirdelectrical contact pair, wherein the fourth electrical contact pair isarranged to close a fourth electrical circuit upon exposure to salivatransported by wicking though at least a portion of the liquidcollection element; the timing element is arranged to receive a signalindicative of closure of the fourth electrical circuit, and is arrangedto generate a third time value indicative of time elapsed between theclosure of the fourth electrical circuit and the closure of one of (a)the first electrical circuit, (b), the second electrical circuit, and(c) the third electrical circuit; and the signaling element arranged togenerate an output signal indicative of state of euhydration, state ofdehydration, or salivary secretion rate of the mammalian subject basedat least in part on the first time value, the second time value, and thethird time value.
 4. An apparatus according to claim 1, comprising aremovable cover arranged over at least a portion of the liquidcollection element.
 5. An apparatus according to claim 1, comprising anelectrolyte arranged to increase conductivity of saliva collected by theliquid collection element.
 6. An apparatus according to claim 1, whereinthe liquid collection element comprises a porous medium or fibrousmedium arranged to absorb saliva.
 7. An apparatus according to claim 1,wherein the signaling element comprises a display.
 8. An apparatusaccording to claim 1, including a processing element or comparatorarranged to divide the predefined liquid holding volumetric capacity bythe first time value to yield a volumetric salivary secretion rate,wherein the output signal comprises a user-perceptible quantitativesignal indicative or correlative of the volumetric salivary secretionrate.
 9. An apparatus according to claim 1, including a processingelement or comparator arranged to compare at least one time value or atleast one value obtainable from the at least one time value with atleast one predefined threshold value, wherein the signaling element isarranged to generate a user-perceptible qualitative signal indicative ofstate of euhydration, state of dehydration, or salivary secretion ratebased at least in part on such comparison.
 10. An apparatus according toclaim 2, including a processing element or comparator arranged tocompare at least one of the time values with at least one other of thetime values, wherein the signaling element is arranged to generate auser-perceptible qualitative signal indicative of state of euhydration,state of dehydration, or salivary secretion rate based at least in parton such comparison.
 11. An apparatus according to claim 1, comprising asampling portion and a monitoring portion, wherein the liquid collectionelement is arranged in the sampling portion, wherein each of the timingelement and the signaling element is arranged in the monitoring portion,and wherein the sampling portion is operatively connected to themonitoring portion via at least one of an electrical communicationcable, an electrical connector, and a wireless communication element.12. An apparatus according claim 1, comprising at least one indicator ortest region arranged to interact with at least one analyte in salivaobtained from the mammalian subject, wherein the at least one indicatoror test region is arranged in fluid communication with the liquidcollection element.
 13. An apparatus according to claim 12, wherein theat least one analyte comprises any of secretory IgA, albumin, secretorycomponent, and aldosterone.
 14. An apparatus according to claim 12,wherein the liquid collection element and the at least one indicator ortest region are arranged in a sampling portion, each of the timingelement and the signaling element is arranged in a monitoring portion,the sampling portion is removably insertable into a monitoring portionto establish electrical communication between the sampling portion andthe monitoring portion, and the monitoring portion comprises an opticalreading element arranged to sense an optical property of the at leastone indicator or test region.
 15. An apparatus according to claim 12,further comprising an optical reading element arranged to generate anelectrical signal correlative of concentration of the at least oneanalyte upon optical interaction with the at least one indicator or testregion.
 16. An apparatus according to claim 15, further comprising asignal processing element arranged to utilize at least one time value incombination with the electrical signal correlative of concentration ofthe at least one analyte to generate an output signal indicative ofstate of euhydration, state of dehydration, or salivary secretion rateof the mammalian subject.
 17. An apparatus according to claim 1,comprising a salivary stimulating agent arranged on or in at least aportion of the apparatus.
 18. A kit comprising an apparatus according toclaim 1 and a salivary stimulating agent arranged for placement into themouth of the mammalian subject prior to or concurrently with placementof the at least a portion of the liquid collection element in fluidcommunication with oral mucosa of the mammalian subject.
 19. A methodutilizing the apparatus of claim 1 for sensing a state of euhydration,state of dehydration, or salivary secretion rate of a mammalian subject.20. A method according to claim 19, further comprising use of the outputsignal to diagnose a disease state of the mammalian subject.
 21. Amethod according to claim 20, wherein the disease state includeshyposalivation as a symptom thereof.
 22. A method according to claim 20,wherein use of the output signal to diagnose a disease state comprisescomparison of the output signal or information derived therefrom with atleast one reference value or reference value range correlative of thedisease state.
 23. A method according to claim 19, further comprisinguse of the output signal to detect a side effect of drug interactionwith the mammalian subject.
 24. A method according to claim 23, whereinuse of the output signal to detect a side effect of drug interactioncomprises comparison of the output signal or information derivedtherefrom with at least one reference value or reference value rangecorrelative of the side effect of drug interaction.
 25. A methodaccording to claim 23, further comprising adjusting dosage oradministration of a drug responsive to the detection of a side effect ofdrug interaction.
 26. An apparatus for sensing a state of euhydration,state of dehydration, or salivary secretion rate of a mammalian subject,the apparatus comprising: a liquid collection element arranged forplacement in fluid communication with oral mucosa in the mouth of amammalian subject, the liquid collection element being liquid permeable,being arranged to transport liquid by wicking, and having a predefinedliquid holding capacity; a salivary stimulating agent arranged forplacement into the mouth of the mammalian subject prior to orconcurrently with placement of the at least a portion of the liquidcollection element in fluid communication with oral mucosa of themammalian subject; at least one first electrode or sensing elementarranged to sense a condition indicative of exposure of a portion of theliquid collection element to oral mucosa in the mouth of a mammaliansubject; at least one second electrode or sensing element arranged tosense a condition indicative of movement by saliva through at least aportion of the liquid collection element; a timing element arranged tobe initiated responsive to receipt of a signal from or detection ofchange of state of the at least one first electrode or sensing element,and to generate a time value indicative of elapsed time since saidinitiation upon receipt of a signal from or detection of a change ofstate of the at least one second electrode or sensing element; and asignaling element arranged to generate an output signal indicative ofstate of euhydration, state of dehydration, or salivary secretion rateof the mammalian subject based at least in part on the time value.